Clip-on magnifiers have been available heretofore, but these were adapted to be mounted on the barrel of a syringe by means of metal clips and usually have been the flat type of magnifier that did not fit around the cylindrical surface of the syringe and consequently did not closely engage the syringe barrel so that it was relatively easy to dislodge the attached unit, possibly causing it to be dropped and if made from glass, easily broken.
It is well known that diabetes causes failing eyesight and since diabetics must utilize great care in determining the number of units of insulin to be injected, it is important that they be able to see clearly the graduations on the syringe barrel. However, the flat type of magnifier previously used, did not make for the most easily read graduations on the cylindrical barrel because it projected beyond the sides of the barrel and did not fit around the barrel so that only the central part of the magnifier along the length of the syringe brought the graduations on the barrel into focus. Further, such glass magnifiers were sensitive to temperature, especially high temperatures and it was necessary to exercise care in sterilizing, or cleaning them.